Examine source code of Flickr Size Pickr

{
  "manifest_version": 2,
  "name": "Flickr Size Pickr",
  "version": "1.2.1resigned1",
  "description": "Adds a context menu to view or download any Flickr photo",
  "author": "Dmitry E.",
  "applications": {
    "gecko": {
      "id": "jid1-3m0VW3IuKlb4Nw@jetpack",
      "strict_min_version": "48.0"
    }
  },
  "icons": {
    "16": "icons/flicker-16.png",
    "32": "icons/flicker-32.png",
    "48": "icons/flickersp-48.png",
    "96": "icons/flickersp-96.png"
  },
  "background": {
    "scripts": [
      "flickr.js"
    ]
  },
  "permissions": [
    "*://www.flickr.com/*",
    "storage",
    "contextMenus",
    "tabs"
  ],
  "options_ui": {
    "page": "options/options.html"
  }
}